It was labeled as made by them, which isn’t necessarily reliable information, considering the incantation you use to activate it. And at one point it’s shown to locate and identify people under the True Cloak of Invisibility, which seems like powerful magic. (It could also be “made” in the sense that they found some sort of magical ingredient or component, ancient and much more powerful than they could make, which the integrated into the map, or even just that they customized an existing map with their silly “access code”.)

And in MoR, Dumbledore himself needed to use the map. Which suggests it was much more powerful than what four of his students could have made.